Various communication systems modify the power of transmitted signals in order to adapt to current channel conditions. Such techniques are commonly referred to as power control. For example, 3rd Generation Partnership Project (3GPP) Evolved Universal Terrestrial Radio Access (E-UTRA) systems apply power control to the uplink signals. The uplink power control methods applied in E-UTRA systems are specified, for example, in 3GPP Technical Specification 36.213, entitled “Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Layer Procedures (Release 8),” (3GPP TS 36.213), version 8.4.0., September, 2008, which is incorporated herein by reference.
E-UTRA is also commonly known as Long-Term Evolution (LTE). An advanced version of E-UTRA, which is commonly known as LTE-Advanced (LTE-A), is currently being specified by the 3GPP standardization bodies. In the context of the present patent application and in the claims, the term “E-UTRA specification” refers to any E-UTRA, LTE or LTE-A specification, as well as to subsequent versions of these specifications.
Uplink power control is useful, for example, for reducing interference and increasing spectral efficiency in cellular communication networks. Some aspects of interference mitigation and spectral efficiency improvement are addressed in a report published by the 3GPP Technical Specification Group Radio Access Network Working Group 1 (TSG-RAN WG1), entitled “Interference Mitigation via Power Control and FDM Resource Allocation and UE Alignment for E-UTRA Uplink and TP,” (R1-060401), Denver, Colo., Feb. 13-17, 2006, which is incorporated herein by reference. Uplink power control in E-UTRA systems is also discussed in TSG-RAN WG1 report R1-070795, entitled “Uplink Power Control for E-UTRA,” Saint-Louis, Mo., Feb. 12-16, 2007, which is incorporated herein by reference.
Some LTE-A systems deploy carrier aggregation techniques, in which a wireless terminal communicates with a base station over multiple aggregated LTE or LTE-A carriers to provide high bandwidth capabilities. Carrier aggregation (also referred to as spectrum aggregation) is described, for example, in TSG-RAN WG1 report R1-082468, entitled “Carrier Aggregation in LTE-Advanced,” Warsaw, Poland, June 30-Jul. 4, 2008, which is incorporated herein by reference.